Photographic processes and products



. E. H. LAND 2,861,885

PHOTOGRAPHIC PROCESSES AND PRODUCTS Filed Nov. 4, 1954 Nov. 25, 1958 Tronspqrenl' Sup p or+ Pholoexposed Silver Halide s'lml'um lo rocesslng Composi, ion Silver-Recep'l'ive Sl'rolum Whi'le Opaque Suppor'l" FIG. I

Composihz Prin+ Viewed by Reflec'l'ion l6 Negol'ive Prinl' in Silver of Low Covering Power 22 Processing Composil'ion Residue I4 PosHive Prin+ in Silver of High Covering Power FIG. 2

24 Processing Composilion Film Applied Silver Receplive Slrul'um FIG. 3

Composi'le Prinl viewed y fieflecfion Waler Absorbenl Sponge Tl 34 i, Nego'live Prin'l in Silver of Low Covering Power Posi'l'lve Prinl' in Silver of High Covering Power HQ 4 INVEN OR BY I am 1 ATTORNEYS United States Patent [will 2,861,885 "PHOTOGRAPHIC PROCESSES AND PRODUCTS Application November4, 1954, Serial N 0. 466,889 4 Claims. (CI, 9629) This-inventionrelates to photographic processes and, more particularly, to silver transfer-reversal processes and their products.

"In a typical silver transfer-reversal process, a silver halidedeveloper and a silver halide solvent are applied, in aqueous alkaline solution, to a-photoexposed silver halide stratum where they develop exposed silver halide to silver and react withunreduced silver halide to form a soluble silver complex. This complex, inorder toform a positive print, is transterred an'd reduced to silver on a silver-receptive stratum upon-Which the silver halide stratumhas been superpose -Ithas been the practice, at the completion of this process, to separate the silverreceptive and silver halide strata in order torenderthe positive print visible.

In accordance with the present invention, the positive print is rendered visible withoutthis separation of the silver halide and silver-receptive strata. It has been recogni'zed (Edwin H. fLand, One Step Photography, Photographic Journal, Section -A, pp. 7 l 5,lanuary 1950) that the silver-receptive stratum may be so constituted as to provide an unusually vigorous silver precipitating environment which causes the silver deposited upon it, in comparison with silver developed in the silver halidestratum, to possessvery high covering power, i. e., opacity per given mass of reduced silver. ;Now it has been found that if; the silver halide is in such a concentration EISIO give rise only, when fully developed, to a predeterminedly lowmaximum'density, and if the silver complex is reduced to silver in a vigorous silverprecipitating environment of the foregoingtype, the resulting negative and positive prints in'superposition provide a composite print that presents agood imageby reflection or projection. Because thesilver halide stratum and the silver-receptive stratum need not be separated, an overall simplification of'the silver transfer-reversal process is achieved and a'protec tive covering for the print is provided.

Accordingly, objects of the present invention are: to provide a photographic processcomprisingthe steps of subjecting a silver halide stratum and a silver-receptive stratum, which are in superposed relation, to a solution of a silver halide developer and a silver halide solventin order to form in the silver halide stratum a negative print in silver of relatively'low covering power and to form in the silver-receptive stratum a positive print in silver of relatively high covering power, and thereafter maintaining thesilver halide stratum and the silver-receptive stratum permanently in superposed relation; and to provide the photographic product of, .thisiprocess.

Other objects of the invention Wlll'il'l part be obvious and will .in part appear hereinafter.

The invention accordingly compris'esrthe' several steps and the relation and order ofone or more of such steps with respeet to each of th'e others, and the produc't possessing the features, properties and the relation of elements which are exemplified in the following detailed disclosure, and the scope of the application of which will be indicated in the claims.

For afullerunderstanding of the nature and, objects of the invention, reference should be had to the following detailed description taken in connection with the accompanying drawings wherein:

Figure 1 is an exaggerated sectional view of photographic elements being processed in accordance withthe present invention;

Fig. 2 is an exaggerated sectional view of the product of the process illustrated in, Fig. 1;

Fig. 3 is an exaggerated sectional view of other photographic elements being processed in accordance with the present invention; and

Fig. 4 is an exaggerated sectional view of the product of the process illustrated inFig. 3.

Figs. 1 and 2 illustrate the spreading of a viscous'alk-aline aqueous solution 10 (Fig. l) of a silver halide developer and a silver halide solvent in a uniformly thin layer between the-adjacent surfaces of a silver halide stratum-12 and a silver-receptive stratum 14, for example by advancing thestrata between a pair of pressure-applying rollers (not shown). Silver halide and silverreceptive strata 12 and 14 are laminated to supports16 andIS respectively. Once applied, solution 10, within a predetermined period, ordinarily of the order of 40 to seconds in duration, forms a negative print in stratum 12 by reducing silverhalide to silver, and, by reacting with unreduced silver halide, forms complexsilver salts which migrate to stratum 14 where they are reduced to silver to form a positive print. In accordance withthe present invention, the solution then is dried in order'to form a more or less solid residue 22 (Fig. 2) which serves as an adhesive to bond silver halidestratum 12 to silverreceptive stratum 14. Either-or both silver halide stratum 12 together with support 16, and silver-receptive stratum 14 together with support 18 are transparent so that the image presented by the superposed negative and positive prints in strata 12 and 14 may be readily observed 'by reflected or transmitted light.

Solution 10, for example, contains a silver halide developer such as hydroquinone, a silver halide solvent such as'sodium 'thiosulfate, and a film-forming material such as a water-soluble polymer, starch or gum. *When'the solution is dried, its residue forms a'firm bondbetween silver halide stratum 12 and silver-receptive stratum 1'4.

Silver-receptive stratum 14 provides one of the vigorous silver precipitating environments described in the copending applications of Edwin H. Land, Serial No. 727,- 3 85, filed February 8, 1947, and'Serial No. 164,908, filed May29, 1950. Such an environment includes silver precipitating nuclei such asthe metal sulfides or selenides,"the colloidal noble metals or organic thio compounds dispersed in a macroscopically continuous vehicle comprising minute, preferably colloidal, particles of a watersoluble, inorganic, preferably siliceous, material such as silica aerogel. Preferably, this stratum ranges from -1 m8 microns in thickness. The positive print is formed in this stratum from fine silver particles concentrated primarily at its surface. Only a minute amount of silver in this condition is'necessary for image formation becauseof its extremely high covering power.

The covering power of silver in a photographic printdepends, in part, upon the concentration, arrangement, size and shape of the silver grains. In a composite print produced as above, the silver deposited by development in silver halide stratum 12 is characteristically different from the silverdeposited by silver complex transfer andreduction in silver-receptive stratum 14. In practice, the covering power of the given mass ofsilver in the positive of silver-receptive stratum 14 ranges from 14 to 15 times-that of an equal mass of silver in the negative of silver halide stratum12. j a

It is apparent that the minimum density of the cornposite print depends, to a substantial extent, upon the maximum density of the negative since the shadows of the negative correspond to the highlights of the positive. If the above-noted ratio of positive silver covering power to negative silver covering power is realized in a composite print to be viewed by reflection, this maximum negative density can be as great as 0.3 without seriously affecting the composite image quality. A substantially higher maximum density is tolerable in the negative when the composite print is used as a transparency because the brightness of the highlights of the composite print is a function of the intensity of illumination. It has been found that a maximum density of as high as 1.0 in the negative is permissible if the maximum density of the composite print is at least 4 times greater. Preferably, then, in a composite image of the foregoing type, the silver halide stratum, when fully developed in any conventional manner, has no greater density than approximately 0.3 if the composite print is to present a reflection image, and has no greater density than approximately 1.0 if the composite print is to serve as a transparency.

Another process embodying the present invention is illustrated in Figs. 3 and 4 where a viscous alkaline solution 23 of a silver halide developer and a silver halide solvent is shown being applied, for example, by means of an absorbent applicator 24, to a laminated photographic product comprising, in sequence, a silver halide stratum 26, a silver-receptive stratum 28 and a support 30. Solution 23 is similar to solution 10, stratum 26 to stratum 12, stratum 28 to stratum 14 and support 30 to support 18.

In practice, assuming that silver halide stratum 26 has been photoexposed, solution 23 reduces exposed silver halide to silver to form in the silver halide stratum a negative print, and reacts with unreduced silver halide to form a water-soluble, complex silver salt which is reduced to silver in order to form a positive print in silver-receptive stratum 28. In the manner described above, the negative print is formed in silver of low covering power and the positive print in silver of high covering power. Thereafter, with silver halide stratum 26 maintained in superposed relation on silver-receptive stratum 28, solution 23 is dried, for example, with the aid of a blotter 34. Support 30 may be either opaque or transparent so that the composite image presented by the positive and negative prints may be observed by reflected or transmitted light.

The present invention thus contemplates a simplified transfer-reversal process which produces a protected transfer-reversal print.

Since certain changes may be made in the above processes and products without departing from the scope of the invention herein involved, it is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.

What is claimed is:

1. A photographic process comprising the steps of subjecting a silver halide stratum and a silver-receptive stratum, which are in contiguous relation, to a thin layer of a processing fluid, said fluid containing a silver halide developer and a silver halide solvent, reacting said silver halide developer with exposed silver halide in said silver halide stratum in order to produce a negative print by reduction of silver halide to silver, reacting said silver halide solvent with unreduced silver halide in said silver halide stratum in order to form a complex silver salt, transferring said complex silver salt to said silver-receptive stratum, reducing said complex silver salt to silver in said silver-receptive stratum in order to form a positive print containing silver, said silver of said positive print being of a first physical character, said silver of said negative print being of a second physical character, a substantial quantity of said silver in said positive print having a higher optical density than an equal quantity of said silver in said negative print, drying said layer of processing fluid to form a laminated unit containing a plurality of strata, said unit being substantially transparent from one of the faces of said unit through one of the silver halideand silver-receptive strata at least to the other of said silver halide and silver-receptive strata, both said positive print and said negative print thereby being visible through said .one of said faces as a composite print.

2. A photographic process comprising the steps of spreading, in a thin layer between a silver halide stratum and a silver-receptive stratum, which are in superposed relation, a substantially transparent solution of a silver halide developer and a silver halide solvent in order to form a unit containing a plurality of strata, reacting said silver halide developer with exposed silver halide in said silver halide stratum in order to form therein a negative print containing silver, reacting said silver halide solvent with unreduced silver halide in said silver halide stratum in order to form a complex silver salt, transferring said complex silver salt to said silver-receptive stratum, re-

ducing said complex silver salt at said silver-receptive stratum in order to form therein a positive print containing silver, said silver of said negative print being of a first physical character, said silver of said positive print being of a second physical character, a substantial quantity of said silver in said positive print having a higher optical density than an equal quantity of said silver in said negative print, said solution containing a film-forming material which, when dry, is securely adherent to said silver halide stratum and said silver-receptive stra 3. A photographic product comprising a laminated unit including a developed, photoexposed silver halide stratum containing a negative print containing silver, a processed silver-receptive stratum having a positive print containing silver, said silver of said positive print being of a 'first physical character, said silver of said negative print being of a second physical character, a substantial quantity of said silver of said first physical character having a higher optical density than an equal quantity of said silver of said second physical character, and a transparent layer sandwiched between said silver halide stratum and said silver-receptive stratum, said transparent layer constituting the dried residue of an alkaline aqueous solution containing a silver halide developer, a silver halide solvent and a film-forming organic polymer, said unit being substantially transparent from one of its outer faces through one of the silver halide and silverreceptive strata at least to the other of said silver halide and silver-receptive strata, both said positive print and said negative print thereby being visible through said one of said faces as a composite print.

4. A photographic process comprising the steps of subjecting a silver halide stratum and a silver-receptive stratum, which are in contiguous relation, to a thin layer of a processing fluid, said fluid, upon being so spread, containing a silver halide developer and a silver halide solvent, reacting said silverhalide developer with ex posed silver halide in said silver halide stratum in order to produce a negative print by reduction of silver halide to silver, reacting said silver halide solvent with unreduced silver halide in said silver halide stratum in order to form a complex silver salt, transferring said complex silver saltto said silver-receptive stratum, reducing said complex silver salt to silver in said silver-receptive stratum in order to form a positive print containing silver, said silver of said positive print being of a first physical character, said silver of said negative print being of a second physical character, said silver-receptive stratum being within the range of from 1 to 8 microns thick, said silver halide stratum being relatively great in thickness with respect to said silver-receptive stratum, said negative image having a maximum density of 1.0, a substantial quantity of said silver in said positive print having a higher optical density than an equal quantity of said silver in said negative print, drying said layer of processing fluid to form a laminated unit containing a 10 plurality of strata, said unit being substantially transparent from one of the faces of said unit through one 5 a complete print.

References Cited in the file of this patent UNITED STATES PATENTS 2,543,181 Land Feb. 27, 1951 2,698,245 Land Dec. 28, 1954 2,712,995 Weyde July 12, 1955 2,726,154 Land Dec. 6, 1955 

1. A PHOTOGRAPHIC PROCESS COMPRISING THE STEPS OF SUBJECTING A SILVER HALIDE STRATUM AND A SILVER-RECEPTIVE STRATUM, WHICH ARE IN CONTIGUOUS RELATION, TO A THIN LAYER OF A PROCESSING FLUID, SAID FLUID CONTAINING A SILVER HALIDE DEVELOPER AND A SILVER HALIDE SOLVENT, REACTING SAID SILVER HALIDE DEVELOPER WITH EXPOSED SILVER HALIDE IN SAID SILVER HALIDE STRATUM IN ORDER TO PRODUCE A NEGATIVE PRINT BY RESOLVENT WITH UNREDUCED SILVER HALIDE IN SAID SILVER HALIDE STRATUM IN ORDER TO FORM A COMPLEX SILVER SALT, TRANSFERRING SAID COMPLEX SILVER SALT TO SAID SILVER-RECEPTIVE STRATUM, REDUCING SAID COMPLEX SILVER SALT TO SILVER IN SAID SILVER-RECEPTIVE STRATUM IN ORDER TO FORM A POSITIVE PRINT CONTAINING SILVER, SAID SILVER OF SAID POSITIVE PRINT BEING OF A FIRST PHYSICAL CHARACTER, SAID SILVER OF SAID NEGATIVE PRINT BEING OF A SECOND PHYSICAL CHARACTER, A SUBSTANTIAL QUANTITY OF SAID SILVER IN SAID POSITIVE PRINT HAVING A HIGHER OPTICAL DENSITY THAN AN EQUAL QUANTITY OF SAID SILVER IN SAID NEGATIVE PRINT, DRYING SAID LAYER OF PROCESSING FLUID TO FORM A LAMINATED UNIT CONTAINING A PLURALITY OF STRATA, SAID UNIT BEING SUBSTANTIALLY TRANSPARENT FROM ONE OF THE FACES OF SAID UNIT THROUGH ONE OF THE SILVER HALIDE AND SILVER-RECEPTIVE STRATA AT LEAST TO THE OTHER OF SAID SILVER HALIDE AND SILVER-RECEPTIVE STRATA, BOTH SAID POSITIVE PRINT AND SAID NEGATIVE PRINT THEREBY BEING VISIBLE THROUGH SAID ONE OF SAID FACES AS A COMPOSITE PRINT. 